[INFO] updating cached repository timmc/cavern
[INFO] running `"git" "fetch" "--all"`
[INFO] [stdout] Fetching origin
[INFO] [stderr] From git://github.com/timmc/cavern
[INFO] [stderr]  * branch            HEAD       -> FETCH_HEAD
[INFO] running `"git" "clone" "work/cache/sources/gh/timmc/cavern" "work/ex/beta-1.38-1/sources/1.37.0/gh/timmc/cavern"`
[INFO] [stderr] Cloning into 'work/ex/beta-1.38-1/sources/1.37.0/gh/timmc/cavern'...
[INFO] [stderr] done.
[INFO] running `"git" "clone" "work/cache/sources/gh/timmc/cavern" "work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/timmc/cavern"`
[INFO] [stderr] Cloning into 'work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/timmc/cavern'...
[INFO] [stderr] done.
[INFO] running `"git" "rev-parse" "HEAD"`
[INFO] [stdout] fb6ebf68efb446fc986137c358b263ab7bef1572
[INFO] sha for GitHub repo timmc/cavern: fb6ebf68efb446fc986137c358b263ab7bef1572
[INFO] validating manifest of timmc/cavern on toolchain 1.37.0
[ERROR] this task or one of its parent failed!
[ERROR] overridden task result to broken:cargo-toml
[ERROR] caused by: missing Cargo.toml for timmc/cavern
[ERROR]